Cleaned up patch as suggested by Vicktor

akka-remote/src/main/scala/remote/RemoteServer.scala

@@ -326,25 +326,28 @@ class RemoteServer extends Logging with ListenerManagement {
   }
 
   private def register[Key](id: Key, actorRef: ActorRef, registry: ConcurrentHashMap[Key, ActorRef]) {
-    if (_isRunning && !registry.contains(id)) {
+    if (_isRunning) {
+      if (registry.putIfAbsent(id, actorRef) eq null) {
         if (!actorRef.isRunning) actorRef.start
-      registry.put(id, actorRef)
+      }
     }
   }
 
   private def registerPerSession[Key](id: Key, factory: () => ActorRef, registry: ConcurrentHashMap[Key,() => ActorRef]) {
-    if (_isRunning && !registry.contains(id)) {
-      registry.put(id, factory)
+    if (_isRunning) {
+      registry.putIfAbsent(id, factory);
     }
   }
 
   private def registerTypedActor[Key](id: Key, typedActor: AnyRef, registry: ConcurrentHashMap[Key, AnyRef]) {
-    if (_isRunning && !registry.contains(id)) registry.put(id, typedActor)
+    if (_isRunning) {
+      registry.putIfAbsent(id, typedActor);
+    }
   }
 
   private def registerTypedPerSessionActor[Key](id: Key, factory: () => AnyRef, registry: ConcurrentHashMap[Key,() => AnyRef]) {
-    if (_isRunning && !registry.contains(id)) {
-      registry.put(id, factory)
+    if (_isRunning) {
+      registry.putIfAbsent(id, factory);
     }
   }
 
@@ -381,7 +384,7 @@ class RemoteServer extends Logging with ListenerManagement {
    * <p/>
    * NOTE: You need to call this method if you have registered an actor by a custom ID.
    */
-  def unregisterPerSession(id: String):Unit = synchronized {
+  def unregisterPerSession(id: String):Unit = {
     if (_isRunning) {
       log.info("Unregistering server side remote session actor with id [%s]", id)
       actorsFactories.remove(id)
@@ -406,7 +409,7 @@ class RemoteServer extends Logging with ListenerManagement {
   * <p/>
   * NOTE: You need to call this method if you have registered an actor by a custom ID.
   */
- def unregisterTypedPerSessionActor(id: String):Unit = synchronized {
+ def unregisterTypedPerSessionActor(id: String):Unit = {
    if (_isRunning) {
      typedActorsFactories.remove(id)
    }
@@ -490,8 +493,8 @@ class RemoteServerHandler(
   val AW_PROXY_PREFIX = "$$ProxiedByAW".intern
   val CHANNEL_INIT    = "channel-init".intern
 
-  val sessionActors = new ChannelLocal[Map[String, ActorRef]]();
-  val typedSessionActors = new ChannelLocal[Map[String, AnyRef]]();
+  val sessionActors = new ChannelLocal[ConcurrentHashMap[String, ActorRef]]();
+  val typedSessionActors = new ChannelLocal[ConcurrentHashMap[String, AnyRef]]();
 
   applicationLoader.foreach(MessageSerializer.setClassLoader(_))
 
@@ -503,8 +506,8 @@ class RemoteServerHandler(
 
   override def channelConnected(ctx: ChannelHandlerContext, event: ChannelStateEvent) = {
     val clientAddress = getClientAddress(ctx)
-    sessionActors.set(event.getChannel(), Map[String, ActorRef]());
-    typedSessionActors.set(event.getChannel(), Map[String, AnyRef]());
+    sessionActors.set(event.getChannel(), new ConcurrentHashMap[String, ActorRef]());
+    typedSessionActors.set(event.getChannel(), new ConcurrentHashMap[String, AnyRef]());
     log.debug("Remote client [%s] connected to [%s]", clientAddress, server.name)
     if (RemoteServer.SECURE) {
       val sslHandler: SslHandler = ctx.getPipeline.get(classOf[SslHandler])
@@ -525,14 +528,12 @@ class RemoteServerHandler(
     val clientAddress = getClientAddress(ctx)
     log.debug("Remote client [%s] disconnected from [%s]", clientAddress, server.name)
     // stop all session actors
-    for ((id, actorRef) <- sessionActors.get(event.getChannel())) {
+    for ((id, actorRef) <- sessionActors.remove(event.getChannel())) {
       actorRef.stop()
     }
-    sessionActors.remove(event.getChannel());
-    for ((id, actorRef) <- typedSessionActors.get(event.getChannel())) {
+    for ((id, actorRef) <- typedSessionActors.remove(event.getChannel())) {
       TypedActor.stop(actorRef)
     }
-    typedSessionActors.remove(event.getChannel());
 
     server.notifyListeners(RemoteServerClientDisconnected(server, clientAddress))
   }
@@ -714,7 +715,7 @@ class RemoteServerHandler(
   }
 
   private def findSessionActor(id: String, channel: Channel) : ActorRef = {
-    sessionActors.get(channel).getOrElse(id, null)
+    sessionActors.get(channel).get(id)
   }
 
   private def findTypedActorById(id: String) : AnyRef = {
@@ -726,7 +727,7 @@ class RemoteServerHandler(
   }
 
   private def findTypedSessionActor(id: String, channel: Channel) : AnyRef = {
-    typedSessionActors.get(channel).getOrElse(id, null)
+    typedSessionActors.get(channel).get(id)
   }
 
   private def findTypedActorByUuid(uuid: String) : AnyRef = {
@@ -767,12 +768,11 @@ class RemoteServerHandler(
       return actorRefOrNull
 
 
-    // the actor has not been registered globally. See if we have it in the session
-
     val sessionActorRefOrNull = findSessionActor(id, channel);
     if (sessionActorRefOrNull ne null)
       return sessionActorRefOrNull
 
+
     // we dont have it in the session either, see if we have a factory for it
     val actorFactoryOrNull = findActorFactory(id)
     if (actorFactoryOrNull ne null) {